The invention relates generally to switching devices, and, more particularly, to a switch device including a lever-side switch contact.
Referring to prior art FIG. 2, a switch device, such as for example a fast direct-current switch, is diagrammatically shown. The switch device comprises a first and a second rigid connection part 5, 4 for connecting a circuit to be switched and a movable contact lever 1 mounted rotatably about an axis 6. On the contact lever 1, there is a contact plate 2 for providing switch contact on the lever side. By actuating the contact lever 1, a contact can be made between the contact plate 2 and a switch contact of the first connection part 5, whereby the circuit is closed across the two connection parts 4 and 5 (cf. switch condition in FIG. 2, in dot-dash lines).
According to the prior art, the contact plate 2 is fixed to the movable contact lever 1, which is electrically connected by way of a flex band 3 for example to the second connection part 4. Instead of the flex band 3, current pins, friction contacts or the like are possible as connecting devices between the contact lever and the second connection part 4. Thus the circuit to be switched in the present example is closed as in FIG. 2 across the two connection parts 4 and 5, the contact lever 1 and the flex band 3.
Points of contact transition in switch devices lead to increased electrical losses and interfere with heat flow. Particularly in the field of opening switch contacts in safety circuit devices, optimal conformation is required. For current limitation, a fast opening of the contact after occurrence of a short circuit is required. The contact lever should be of such conformation as to meet the following mechanical and electrical requirements.
In mechanical regard, the contact lever should exhibit a minimal mass inertia, in order to make possible a fast switching operation. A required high current capacity results in a maximal contact lever cross-section and a minimal specific resistance of the contact lever material as electrical requirements.
From the aforementioned requirements, however, it is apparent that an improvement in mechanical properties generally leads to an impairment of the electrical properties, and vice versa.
In an exemplary embodiment of the invention lever-side switch contact is arranged on a connecting device to provide a switch, the function of conducting current and heat is separated from the function of contact guidance. Thus the contact lever performs purely mechanical guidance functions, so that the requirements imposed on it as to current capacity are eliminated. Owing to the separation of the current conductive function from the contact guiding function, the contact lever may be produced in light-weight construction with low mass inertia, from electrically non-conductive material for example.
The conformation of the switch device of the invention permits the use of a relatively long, flexible connecting device such as for example a flex band, whereby a conformation having a positive influence on service life can be realized.
Further, the reduction of contact transition points and the direct connection of the lever-side switch contact to the connection device achieve a high thermal and electrical conductivity.